A 3D temperature field reconstruction method using the colored background oriented schlieren(CBOS)method is proposed to address image blurring due to the different refractive index of the multi-wavelength light and si...A 3D temperature field reconstruction method using the colored background oriented schlieren(CBOS)method is proposed to address image blurring due to the different refractive index of the multi-wavelength light and significant errors produced when the traditional background oriented schlieren(BOS)method is applied to high-temperature gas.First,the traditional method is employed to reconstruct the non-uniform 3D temperature field.Second,the CBOS method is applied to correct the distortion.Then,by analyzing the correlation coefficient among different color points of the colored background pattern,the non-uniform temperature field is reconstructed much more accurately.Finally,the experimental results are verified by applying the Runge-Kutta ray-tracing method and the thermocouple contact measurement method.The maximum average temperature error of the CBOS-reconstructed temperature field is 12.92°C,compared with the thermocouples.Therefore,an accurate three-dimensional reconstruction of the temperature field can be achieved by the proposed method effectively.展开更多
A new method for visualizing sound propagation in solids and liquids is described in this paper. The method can show the sound propagation process dynamically in two dimensions. Compared with Schlieren method and dyna...A new method for visualizing sound propagation in solids and liquids is described in this paper. The method can show the sound propagation process dynamically in two dimensions. Compared with Schlieren method and dynamic photo-elastic method, this method cannot only show the sound field distribution in liquid and solid at different time moments, but also can be applied to non-transparent solid. In addition, it does not strictly require small residual stress of the sample. The sample can, therefore, be easily made. Because the acoustic field is obtained by indirect measurements, the recording can be affected by the after-shock of the receiving sensor and is prone to the influence of the direct wave of the liquid. Putting an aluminum plate into a liquid, we recorded the compression wave, shear wave and surface wave in the aluminum and, in the liquid we also recorded the direct wave and three head waves, which are directly coupled with the compression wave, shear wave and surface wave respectively. The recording clearly depicts the coupling relationship of the sound waves through the interface between the aluminum and the liquid. Putting a plexiglass into a liquid, we also recorded the sound waves in the plexiglass and the coupling relationship between the sound waves in the two mediums.展开更多
An experimental system based on the background-oriented schlieren（BOS） technique is built to reconstruct the density and temperature distribution of a flame-induced distorted flow field which has a density gradient....An experimental system based on the background-oriented schlieren（BOS） technique is built to reconstruct the density and temperature distribution of a flame-induced distorted flow field which has a density gradient. The cross-correlation algorithm with sub-pixel accuracy is introduced and used to calculate the background-element displacement of a disturbed image and a fourth-order difference scheme is also developed to solve the Poisson equation. An experiment for a disturbed flow field caused by a burning candle is performed to validate the built BOS system and the results indicate that density and temperature distribution of the disturbed flow field can be reconstructed accurately. A notable conclusion is that in order to make the reconstructed results have a satisfactory accuracy, the inquiry step length should be less than the size of the interrogation window.展开更多
基金Supported by the National Natural Science Foundation of China(52005500)Foundation of Tianjin Educational Committee(2018KJ242)Basic Science-Research Funds of National University(3122019088)。
文摘A 3D temperature field reconstruction method using the colored background oriented schlieren(CBOS)method is proposed to address image blurring due to the different refractive index of the multi-wavelength light and significant errors produced when the traditional background oriented schlieren(BOS)method is applied to high-temperature gas.First,the traditional method is employed to reconstruct the non-uniform 3D temperature field.Second,the CBOS method is applied to correct the distortion.Then,by analyzing the correlation coefficient among different color points of the colored background pattern,the non-uniform temperature field is reconstructed much more accurately.Finally,the experimental results are verified by applying the Runge-Kutta ray-tracing method and the thermocouple contact measurement method.The maximum average temperature error of the CBOS-reconstructed temperature field is 12.92°C,compared with the thermocouples.Therefore,an accurate three-dimensional reconstruction of the temperature field can be achieved by the proposed method effectively.
基金Tianjin University's 985 Talent Plan, Key Project Science and Technology from Zhongyuan Oil Field and National Natural Science Foundation of China (50479070).
文摘A new method for visualizing sound propagation in solids and liquids is described in this paper. The method can show the sound propagation process dynamically in two dimensions. Compared with Schlieren method and dynamic photo-elastic method, this method cannot only show the sound field distribution in liquid and solid at different time moments, but also can be applied to non-transparent solid. In addition, it does not strictly require small residual stress of the sample. The sample can, therefore, be easily made. Because the acoustic field is obtained by indirect measurements, the recording can be affected by the after-shock of the receiving sensor and is prone to the influence of the direct wave of the liquid. Putting an aluminum plate into a liquid, we recorded the compression wave, shear wave and surface wave in the aluminum and, in the liquid we also recorded the direct wave and three head waves, which are directly coupled with the compression wave, shear wave and surface wave respectively. The recording clearly depicts the coupling relationship of the sound waves through the interface between the aluminum and the liquid. Putting a plexiglass into a liquid, we also recorded the sound waves in the plexiglass and the coupling relationship between the sound waves in the two mediums.
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.NSFC 91441205)
文摘An experimental system based on the background-oriented schlieren（BOS） technique is built to reconstruct the density and temperature distribution of a flame-induced distorted flow field which has a density gradient. The cross-correlation algorithm with sub-pixel accuracy is introduced and used to calculate the background-element displacement of a disturbed image and a fourth-order difference scheme is also developed to solve the Poisson equation. An experiment for a disturbed flow field caused by a burning candle is performed to validate the built BOS system and the results indicate that density and temperature distribution of the disturbed flow field can be reconstructed accurately. A notable conclusion is that in order to make the reconstructed results have a satisfactory accuracy, the inquiry step length should be less than the size of the interrogation window.
